Since I can't seem to find a product by Krylon called "Iridescent-It!", I'm a bit stuck as to how to get this kind of look. It's for armor, and the base is mostly black with a silver faded trim. It has a sheen but no color, which is why I was looking for an iridescent spray, so it wouldn't run over the silver or the black and drown it out when I use it.

Does it have to be a spray paint? I've used Delta's iridescent glass paint in the past and know that it looks nice and goes on translucent (it IS glass paint, after all!). One of the white iridescent paints should give you a good translucent coat with a iridescent sheen. The only problem is that this paint can be a little hard to find, as it seems it's not available at some stores anymore. Martha Stewart's line of glass paints has been pretty good though. If you can't find Delta and see an iridescent glass paint from the Martha Stewart brand, I would give that a shot. This will only be seen when the light hits it though. Otherwise, it will just look like the color under it.

Otherwise, if there is an acrylic paint you think would work, you could always mix a drop of it with acrylic medium to get it translucent. This will basically just give you a very slightly pigmented version of the acrylic paint (you can tweak the ratio to your liking).

To make sure we're on the same page, iridescent effects are those little rainbowish sparklies that shimmer in pink, purple, and light blue and emerald. It is effect seen in soap bubbles and spills.

Iridescent powder pigment can often be found in the craft store. (Curiously, it is often found in or near the scrapbooking isle). You can mix this with a clear acrylic paint such as mod-podge and apply it via brush, airbrush (not microns!), or spraygun. Once the paint has fully dried, buff the surface briskly with a soft cloth to see the full effect.

You'll want to do some tests to determine just what concentration of pigment you want. A little goes a long way. Just mix it thoroughly. Start with a tiny bit of paint. add a pinch of pigment (use a spoon or stick), mix it up, then slowly add more paint while continuing to mix. Mix some more if you allow the paint to settle.

You might also want to consider opalescent pigments. They produce pretty spiffy effects too. Same process.